This week's two installments of NBC's "America's Got Talent" will be crucial for 9-year-old Tallan Latz, the guitar prodigy from Elkhorn who made it through the auditions on the top-rated summer talent competition.

Starting with Tuesday's installment, airing at 8 p.m. on Channel 4, eliminations begin in Las Vegas as the judges whittle down the crowd to the top 40.

Final decisions on that group will be made by the end of Wednesday's 8 p.m. show. Tuesday's show repeats at 7 p.m. Wednesday, so you could watch them back to back.

The talented Tallan is a good bet to make it past the judges to face viewer votes as the competition for a $1 million cash prize moves into the next phase.

All three judges were enthusiastic about the pint-sized guitarist, who's been playing since he was 5.

Unlike "American Idol," this is as much about the curiosity factor of the performers, and a 9-year-old guitar whiz, especially a telegenic one like Tallan, is an obvious contender, among a bunch of novelty acts and a few genuine talents.

Tallan is scheduled to appear on the WKLH-FM (96.5) morning show on Wednesday, according to his MySpace page.

CHANNEL SURFING: Outside the summer numbers posted by "AGT" and a few other bright spots, NBC's ratings have been in the trash lately. The guy who gets a lot of the credit for embarrassing bombs such as the "Knight Rider" and "Bionic Woman" remakes, Ben Silverman, is out as co-chairman of NBC Entertainment and Universal Media Studios.

• This fall's 21st season of "The Simpsons" will feature Sarah Silverman, Coldplay's Chris Martin and the late Eartha Kitt as guest voices.

• Popular Mechanics reports that Jamie Hyneman and Adam Savage of the Discovery Channel's "Mythbusters" show will edit the September issue of the magazine. The issue is out Aug. 11, details are available at www.popularmechanics.com.

• Elizabeth Mitchell is returning to ABC's "Lost," which she left after the first season. Michael Ausiello reports at ausiellofiles.ew.comthat she's thanking fans for her return. She'll also be in ABC's "V" remake, due to launch in midseason.

• The British tabloid The Sun says "Britain's Got Talent" judge Amanda Holden will join CBS' "Early Show." It says her first assignment will be to interview Simon Cowell, the creator of "BGT" as well as a judge on that show and "Idol."

• With Keith Olbermann on vacation, his chair on MSNBC's "Countdown" will be filled by Howard Dean on Tuesday and Wednesday at 7. Olbermann returns Monday.

A SUPER DUPER CRITIC: The Washington Post is moving longtime TV critic Tom Shales into a new column, allowing him to critique broader culture. He's been writing about television for 30 years and is one of the most respected TV critics out there.

Post veteran Hank Steuver is the paper's new TV critic, and Lisa DeMoraes will continue to write about the TV biz.